The primary aim of this study will be to examine whether a chronic-care obesity intervention delivered in a "stepped-care" manner, results in improved weight loss compared to a standard behavioral weight loss intervention (SBWP group). It is hypothesized that there will be a significant increase in weight loss following an 18-month intervention in Stepped-Care versus SBWP. Secondary outcomes include body fat distribution, process measures of energy intake and physical activity, and behavioral/psychosocial measures that may be influence by the proposed interventions. In additional, a cost analysis will be performed to evaluate these interventions. The prevalence of overweight and obesity have been increasing over the past few decades, and it is now estimated that in excess of 65 percent of adults have a BMI >30 kg/m2. It has been suggested that a chronic care intervention in which there is continued contact between the interventionist and the weight loss participate be implemented to improve long-term weight loss outcomes. In addition, it has been suggested that a model to consider for modifying health-related behaviors is a "stepped-care" intervention, which increases the intensity and frequency of contact between the participant and the interventionist. However, the stepped-care approach has not been systematically and extensively applied to behavioral weight control interventions. This study will randomly assign 356 participants to either 1) standard behavioral weight loss program, 2) stepped-care weight loss program. The length of the intervention will be 18 months with assessments occurring at 0, 3, 6, 9,12,15, and 18 months. The stepped-care intervention will be evaluated based on the ability of the participant to achieve a predetermined weight loss goal at each assessment period. If the goal is achieved, the participant will continue with that intervention step for an additional 3 months. If the weight loss goal is not achieved, the participant is progressed to the next step which increases the intensity and frequency of the contact between the interventionist and participant. If successful, a stepped-care intervention model may have application in various health-care settings and may be appealing to health-care providers and managed care organizations by providing a criterion-based intervention to improve long-term weight loss.